This project proposes to contribute to the understanding of the structure and function of avian retrovirus RNAs. The objectives of this research are: 1) To determine the role of internals and 5'-terminal RNA methylation in the processing of avian sarcoma virus RNA. The effects of in vivo RNA methylation inhibitors on the fidelity and extent of splicing of viral RNA will be studied; the location of the internal methylations will be determined, and the extent of methylation of the intracellular RNA will be compared to the genome RNA; 2) To further compare the 5'-terminal leader sequence and 3'-terminal sequences of the subgenomic viral mRNAs to the genome RNA 5'-leader sequence by hybridization of viral RNAs to cloned fragments of viral DNA, digestion of the hybrids with S1 nuclease, and analysis of the DNA fragments on polyacrylamide gels; 3) To determine the precursor-product relationships among the various species of viral-specific RNA. Pulse-chase experiments with radioactive RNA precursors will be carried out and viral-specific RNA will be isolated by hybridization to viral-specific DNA which is covalently linked to cellulose.